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Unformatted text preview: nderstanding of the visual
system. Highlights basic properties of the visual
system, outline of what we will be covering
today: Transducing Light Energy Into a Neural Signal!
In darkness, a rod continuously
releases glutamate. !
When light is absorbed by rhodopsin
in the outer segment, it breaks down a
G-protein and initiates a cascade of
chemical events that closes Na+
channels. One photon of light can shut
off a million Na+ from entering. This
hyperpolarizes the cell. !
The size of the hyperpolarizing potential determines
the magnitude of the reduction in the release of
The whole visual system tries to enhance the light in particular ways, like
enhance lines, contours, so that we can distinguish things apart. Hyperpolarizing the photoreceptor causes them to
release less glutamate, which depolarizes the on-center
bipolar cell and hyperpolarizes the off-center bipolar
cell. Glutamate always depolarizes ganglion cells, so
there is increased ﬁring in the on-center ganglion cell
and decreased ﬁ...
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This note was uploaded on 01/18/2014 for the course PSY 123 taught by Professor Staff during the Fall '11 term at UCSB.
- Fall '11